48 (Heparan sulfate proteoglycan)Figure 1 Model of interaction between FGF, its receptor, and the proteoglycan carbohydrate groups. Data support the hypothesis that HSPGs modulate the binding of FGF-2 to FGFR through the formation of a ternary complex in which the glycosaminoglycan chain interactswith FGF-2 via 2-O- and N-sulfate groups while 6-O-sulfate groups are required for its interaction with FGFR. A single molecule of heparin/HS may bind several molecules of FGF-2 suggesting that GAG induces oligomerization of FGF-2. (After Presta, M. 2000).